Ground working tools are commonly used for a variety of purposes in farming, chiefly cultivation and plowing. Certain soils, however, are heavy with obstructions such as rocks and tree stumps and the ground working tools are subject to damage or destruction if they contact these obstacles. When a blade cultivator is used, the damage can be particularly burdensome because the blade is large and expensive to replace.
There are a variety of trip mechanisms available for use on implements with ground working tools. Most of these trip mechanisms were designed, however, for implements other than blade cultivators. Blade cultivators are particularly demanding on trip mechanisms because of their size and cost. Even those trip mechanisms designed for blade cultivators, however, have drawbacks.
Perhaps the trip mechanism most relevant to the present invention which is part of the prior art is the apparatus disclosed in U.S. Pat. No. 3,789,928 (Nja). The trip mechanism used in that patent is particularly for mouldboard plows and, therefore, certain of the features have reduced utility for cultivators. One feature is the configuration of the bolt mounting. This is so because the mouldboard plow is relatively narrow as compared to a blade cultivator wherein it is desirable to move the blade back, up or to the side depending on where on the blade the obstacle is encountered. The mounting configuration described in the present application is designed to achieve a minimum blade displacement when obstacles are encountered. Further, there are force adjustments which can be made on the present mechanism which are not available on the apparatus disclosed in the Nja specification.